Adaptive mirror comprising cooling channels

ABSTRACT

A mirror, in particular an adaptive mirror configured as a laser beam guidance component. The mirror comprises a housing, to which a mirror element that is optionally deformable is allocated. The aim of the invention is to construct the mirror element with an oval, in particular elliptical shape.

BACKGROUND OF THE INVENTION

The invention relates to a mirror, in particular an adaptive mirror as alaser beam guidance component, having a housing which is assigned amirror element, the mirror element possibly being designed to bedeformable.

Game of this type are known and can be obtained in an extremely widerange of forms and designs on the market. They are used substantially aslaser beam guidance components for deflecting laser light. In this case,round mirrors are known on the market and likewise can be designed to bedeformable in order to perform adjustment of the laser beam.

The disadvantage here is that exact adjustment of different wavefrontsand divergences between incident and reflective laser light is carriedout only inadequately by a curving of round mirrors.

If a round mirror is deformed, then its mirror surface is curved outwardor inward in sections.

Differences in the wavefront cannot be adjusted exactly, nor divergencescompensated for, in this way. This leads in particular to changes in thefocal point and to undesired changes in the laser beam, in particularits wavefront.

The present invention is based on the object of providing a mirror, inparticular an adaptive mirror of the type mentioned at the beginning,which eliminates the aforementioned disadvantages and with which, in asimple and effective manner, divergences between incident and emergentlaser light on a mirror surface, in particular on a mirror element, canbe adjusted, the intention also being to exert an influence on theappropriate wavefronts.

SUMMARY OF THE INVENTION

the foregoing object is achieved by a mirror element which is oval,preferably elliptical.

In the present invention, it is important that the mirror, in particularits diaphragm, is oval. In this case, the mirror element has an overalllength and width which differ. The overall length and the width of themirror element are in a relationship with the angle of the incidentand/or emergent laser light, based on a mid-axis which is perpendicularto the surface and/or based on a transverse axis of the mirror element.

In particular as a result of the oval shape of the mirror element, givenappropriate deformation, this is curved, in particular around the regionof the transverse axis and longitudinal axis, as a controllable adaptiveoptical unit.

As opposed to round mirrors, curvature is not carried out in the mannerof a spherical section or a half-shell section but approximatelyhomogeneously in the region of the mid-axis, differently about thetransverse axis and longitudinal axis. The result of different lengthsof transverse axis and longitudinal axis, is different radii.

It is just this effect which permits divergences in laser light incidentat an angle on the surface of the mirror element to be adjusted.

Since the angle of incidence or emergence of such a mirror, inparticular such a laser beam guidance component, is a fixed variable, onthe basis of this variable the mirror may be set in accordance with itsoverall length and width in the ratio overall length is equal to thewidth divided by cosine squared angle of incidence and/or emergence.

In this way, quite specific angles of incidence and/or emergence, forexample 45°, 30°, 15° to a perpendicular mid-axis of the mirror surface,the width and overall length of the mirror element can be determined anddefined. Depending on these angles, the oval elliptical shape of themirror element is then produced or adapted. In this way, a mirrorelement is provided with which divergences and wavefronts can beinfluenced in a simple way, if the mirror element is designed as anadaptive optical unit, in particular as a deformable mirror. To thisend, the mirror element can be formed from a single diaphragm or aplurality of individual diaphragms, which if appropriate can be cooleddirectly via cooling ducts. However, the cooling can also be carried outotherwise here. In the preferred exemplary embodiment, however, coolingducts are provided in the region of the mirror surface, in particular inthe region of the diaphragm, in order to cool the surface directly andpermanently, independently and decoupled from an actuator for deformingthe mirror element permanently.

The foregoing provides a mirror element which may be set adaptively bymeans of different actuators, it being possible for divergences andwavefronts to be changed or adjusted in particular as a result of itsoval shape.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and details of the invention emerge fromthe following description of preferred exemplary embodiments and byusing the drawing wherein:

FIG. 1: shows a side view of a deformable mirror, in particular of anadaptive mirror;

FIG. 2: shows a longitudinal section through the deformable mirror inthe region of a diaphragm, in particular in the region of cooling ductsalong the line II—II according to FIG. 1;

FIG. 3: shows a schematically illustrated cross section through thedeformable mirror according to FIG. 1 along the line III—III;

FIG. 4: shows a cross section of the mirror according to FIG. 1 as afurther exemplary embodiment;

FIG. 5: shows a schematically illustrated plan view of a mirroraccording to the invention, in particular a deformable mirror;

FIG. 6: shows a schematically illustrated side view of the mirroraccording to FIG. 5 with individual laser beams indicated dashed.

DETAILED DESCRIPTION

According to FIG. 1, a deformable mirror R₁ has a housing 1 which isformed from a baseplate 2, an adjacent cylinder wall 3 and a mirrorelement 4 closing it on the front side. The mirror element 4 has apolished surface 5 for deflecting incident laser light.

In particular in order to influence the laser light which is incident onthe surface 5, the mirror element 4 is deformable, in particularadaptive.

As emerges in particular from the cross-sectional illustration accordingto FIG. 3, the mirror element 4 comprises at least one diaphragm 6.1,6.2, the diaphragm 6.1 forming the abovementioned surface 5.

The mirror element 4 is preferably formed in two parts as a diaphragm6.1, 6.2, a plurality of cooling ducts 7.1, 7.2 being assigned to themirror element 4, in particular the diaphragm 6.2, in the preferredexemplary embodiment.

As indicated in particular dashed in FIG. 1, the cooling ducts 7.1, 7.2are fed via a feed 8 and a discharge 9, feed 8 and discharge 9 reachingthrough the baseplate 2 and opening via the cylinder wall 3 into themirror element 4, in particular in the cooling ducts 7.1, 7.2 of thelatter. Feed 8 and discharge 9 are preferably located on a longitudinalaxis L of the diaphragm 6.2 and are preferably arranged at the end.

In the preferred exemplary embodiment according to FIG. 2, the mirrorelement 4, in particular the diaphragm 6.1, 6.2, is oval, a longitudinalaxis L being greater than a transverse axis Q.

A further special feature of the present invention is that theindividual cooling ducts 7.1 run parallel to one another and arearranged at a distance from one another and form an angle α of about 30°to 60°, preferably of 45°.

The cooling ducts 7.2 preferably run at right angles and at the samedistance likewise parallel to the cooling ducts 7.1 and form an angle βof about −30° to −60°, preferably −45°, to the to the transverse axis Q.

As a result, rectangular web elements 10, which space the respectivediaphragms 6.1, 6.2 apart, are produced between the respective coolingducts 7.1, 7.2.

In order that the mirror element 4, in particular the diaphragms 6.1,6.2, may be deformed continuously and homogeneously over the completesurface, the diaphragms 6.1 and 6.2 are connected firmly to eachanother, in particular by a form fit.

As emerges from FIG. 3, an internal space 11, which is used toaccommodate actuators or the like (not illustrated here), is formedbetween the mirror element 4, the cylinder wall 3 and the baseplate 2.In the preferred exemplary embodiment, an opening 12 is formed in thebaseplate 2, in which, for example, a compressible or preferably anincompressible medium, such as water or oil, is put and, by means of theapplication of pressure or vacuum, the mirror element 4 is deformed, themembrane 6.1, 6.2 in particular being curved outward when pressure isapplied to the mirror element and curved inward when a vacuum isapplied. In this way, for example, the focusing position of a laserwhich is incident on the surface 5 of the mirror element 4 isinfluenced.

In a further exemplary embodiment according to FIG. 4, it is shown thatthe individual cooling ducts 7.1, 7.2 can be provided either in thediaphragm 6.1 and/or in the diaphragm 6.2. These can also be provided soas to overlap in the two diaphragms 6.1, 6.2, it being possible for thelatter to be designed with a cross section that is rectangular, curved,semicircular and, in the event of an overlap, round. No limit is to beplaced on the invention here.

Furthermore, the scope of the present invention is also to includeinserting, for example, mechanically, pneumatically, hydraulically orpiezoelectrically operated actuators or the like in the internal space11, in order to deform the diaphragm 6.1, 6.2 and the mirror element 4.

However, it is important that a mirror surface 5, in particular thediaphragm 6.1, is directly very well cooled, in order in particular tocool the service life by means of this direct cooling of the surface,irrespective of any desired actuators for deforming the mirror element.

In this case, the scope of the present invention is also to includebeing able to arrange the cooling ducts in the longitudinal directionand/or in the transverse direction or at any desired angles α and β inthe diaphragms 7.1, 7.2. The present invention is not to be restrictedto this.

According to FIG. 5, the mirror R₁ is shown as a plan view, in which themirror element 4 is oval according to the invention. In this case, themirror element 4 has an overall length G which is substantially greaterthan a width B.

It is also important in the present invention, in particular if if themirror R₁ is constructed as an adaptive mirror, that its surface 5 bedeformable in the manner described above. By means of the deformation ofthe oval surface, different wavefronts which may be deflected orreflected in the form of laser light at an angle of incidence and/oremergence γ, based on a normal to the surface, for example to a mid-axisM of the mirror element 4 on its surface 5, may be influenced.

In particular via the deformation of the oval mirror surface, the laserbeam which strikes a surface 5 will be diverged differently, it beingpossible for its divergence to be influenced at the same time by thecurvature. In particular in the region of the centre M, an oval mirroris curved substantially homogeneously and uniformly.

In this case, a proven relationship between an overall length G and thewidth B of the mirror element 4, as a function of the angle of incidenceγ to a mid-axis M or to the normal to the surface, is for the overalllength G to be the width B divided by (cos² γ) (G=B/(cos² γ)).

If, for example, the angle of incidence and/or emergence γ to theperpendicular mid-axis M to the surface of the mirror element 4 changes,then the appropriate ratio between the width B and overall length G maybe determined via this function G=B/(cos² γ). The angle of incidence γis fixedly predefined for each mirror element, and the overall length Gand the width B is in each case determined and designed for thispurpose. As illustrated in particular in FIG. 6, individual lightwaves13 are shown which on one side strike the mid-axis M centrally and,outside the latter, strike a surface 5 and are reflected by this. Inthis case, the angle of incidence and/or emergence γ, based on aperpendicular mid-axis M to the surface 5, is chosen to be 45° in thepreferred exemplary embodiment.

If, for example, this angle γ changes, if this is selected to be largeror smaller, then differences arise in the wavefront of the incident andof the emergent laser light.

In order to select an appropriate curvature and shape of the mirrorelement optimally in a relationship with the angle γ, the oval shape ofthe mirror element 4 is used in the manner described above, the width Bbeing related as described above with the overall length G as a functionof the angle γ. In this way, for any desired angle γ, an optimum mirrorR can be designed which can be adapted to this designed or predefinedangle γ. In this way, the quality of the wavefront can also bemaintained. Only the divergence of the wavefront may be influenced.

1. A mirror for a laser beam guidance component comprising a housing, a deformable mirror element in the housing, the deformable mirror element comprises at least one oval diaphragm formed of two parts, the oval diaphragm is provided with first and second cooling ducts having a first and second arrangement respectively, the first arrangement runs parallel at a distance from one another and the second arrangement runs perpendicular to the first arrangement so as to form a web pattern, wherein the first cooling duct forms an angle (α) of between 30° to 60° to a transverse axis (Q) of the mirror element and the second cooling duct forms an angle (β) of between −30° to −60° to the transverse axis (Q).
 2. The mirror as claimed in claim 1, wherein the cooling ducts are connected to at least one feed.
 3. The mirror as claimed in claim 2, wherein the feed and a discharge for the cooling ducts are in each case provided at an end and opposite one another in the mirror element.
 4. The mirror as claimed in claim 3, wherein the feed and discharge are provided in respective end regions of the mirror element, in the region of a longitudinal axis (L).
 5. The mirror as claimed in claim 3, wherein the at least one diaphragm is adjoined by a circumferential cylindrical wall which is connected to a baseplate (2), wherein an internal space is formed between the cylinder wall, the baseplate and the diaphragm.
 6. The mirror as claimed in claim 5, wherein the discharge and the feed run through the baseplate and through the cylinder wall and connect to the cooling ducts.
 7. The mirror as claimed in claim 5, wherein the internal space has pressure applied to it by one of pneumatically, hydraulically, and piezoelectrically means for the purpose of deformation.
 8. The mirror as claimed in claim 1, wherein a width (B) and an overall length (G) of the mirror element is selected as a function of an angle of incidence (γ) of laser light on a surface of the mirror element.
 9. The mirror as claimed in claim 8, wherein the width (B) is less than the overall length (G).
 10. The mirror as claimed in claim 9, wherein a ratio between the overall length (G) and the width (B) of the mirror element is set to be (G=B/cos² γ).
 11. The mirror as claimed in claim 10, the angle (γ) forms an angle of incidence and angle of emergence between a perpendicular mid-axis (M) to the surface of the mirror element.
 12. The mirror as claimed in claim 11, wherein at the angle of incidence (γ), the ratio of overall length (G) and the width (B) is calculated in accordance with (G=B/(cos² γ).
 13. The mirror as claimed in claim 1, wherein the first and second cooling ducts are provided in one or more parts of the diaphragm of the mirror element.
 14. The mirror as claimed in claim 1, wherein the web pattern runs diagonally to a longitudinal axis (L) and to the transverse axis (Q) of the mirror element (4).
 15. The mirror as claimed in claim 1, wherein the at least one diaphragm has pressure applied to it by one of mechanically, pneumatically, hydraulically, and piezoelectrically means for the purpose of deformation.
 16. The mirror as claimed in claim 1, wherein the cooling ducts are formed with a cross section which is one of rectangular, oval, round and a section of a part circle.
 17. The mirror as claimed in claim 1, wherein the mirror element can be deformed independently an cooled separately and independently. 